Circuit employing electronic or semiconductor switch regulating an output voltage



Sept. 21, 1965 R. H. PINTELL 3,207,975

CIRCUIT EMPLOYING ELECTRONIC OR SEMICONDUCTOR SWITCH REGULATING AN OUTPUT VOLTAGE Filed May 51. 1960 2 Sheets-Sheet l FIG.3

Robert H.Pintell INVENTOR.

AGENT.

R H. PINTELL Sept. 21, 1965 CIRCUIT EMPLOYING ELECTRONIC 0R SEMICONDUCTOR SWITCH REGULATING AN OUTPUT VOLTAGE Filed May 31, 1960 2 Sheets-Sheet 2 Rober? H.Pintell INVENTOR.'

United States Patent CIRCUIT EMPLOYING ELECTRONIC OR SEMI- CONDUCTOR SWITCH REGULATING AN OUTPUT VOLTAGE Robert H. Pintell, Bronx, N.Y., assignor to Intron International, Inc., Bronx, N.Y., a corporation of New York Filed May 31, 1960, Ser. No. 32,976 15 Claims. (Cl. 323-22) My present invention relates to a regulator circuit of the type disclosed in my copendiug application Ser. No. 834,847 filed August 19, 1959, now abandoned, of which the instant application is a continuation-in-part, and has as its primary object the extension of the principles of that co-pending application to other regulator circuits.

It is a more specific object of the invention to provide means for stabilizing the output of a thyratron, controlled rectifier, or other unidirectional element used for the control of an alternating or direct current energizing a load.

Another object of the invention is to provide an improved constant-current or constant-voltage regulator circuit utilizing a single unidirectional control element.

A feature of my invention resides in the provision of a branched transmission circuit including valve means for the conversion of an alternating-current input into a rawrectified or pulsating unidirectional current. The transmission circuit comprises at least one branch, common to the paths of both halves of each alternating-current cycle, which is provided with a unidirectionally efiective control element adapted to pass all or only part of each pulse of the unidirectional current. Advantageously, such valve means may take the form of a plurality of metallic, crystallic, vacuum-tube or other rectifiers connected in a full-wave bridge circuit, with the unidi-rectional'ly effective control element inserted in one diagonal of the bridge, between the D.-C. terminals thereof, while the alternating-current source is connected across the other diagonal. An alternating-current load may be connected in series with the A.-C. source, i.e. in the driving circuit which energizes the bridge, whereas a direct-current load is conveniently connectable in series with the control element between the D.-C. terminals of the bridge. The control element is preferably a triggerable electnonic switch, such as a thyratron or a controlled rectifier. I have found that the use of the latter type of element, in combination with feedback means for varying the duration of the conductive or on periods of the switch, makes it possible to control highvoltages and/or largercurren-ts with a minimum of dissipation.

According to a more specific feature of the invention I provide means for triggering the operation of the electronic switch .at the cadence of the alternating-current input and feedback means adapted to delay or to advance its triggering so that a substantially constant voltage or current is passed to the load. I have also found it advantageous to employ a differentiation circuit to produce a relatively steep wavefront or pulse at the alternatingcurrent cadence for triggering the electronic switch. The feedback means may include an amplifying connection, e.g. in the form of a winding on a saturable core of an electromagnetic transducer such as a reactor or a mag netic amplifier.

The above and other objects, features and advantages of my invention will become more readily apparent from the following detailed description, reference being made to the accompanying drawing in which FIGS. l-5 represent circuit arrangements of various embodiments according to the invention, FIG. 6 being a set of graphs illustrating the various wave shapes present in different parts of these systems.

FIG. 1 shows an embodiment of my invention wherein a rectifier bridge 100, comprising rectifiers 101, 102, 103, 104, is provided with a solid-state controlled rectifier 105 and a protective choke 116 serially inserted in one bridge diagonal. The gate of rectifier element 105 is returned to its cathode via a control circuit which includes a fullwave auxiliary rectifier 124 and a resistor 108 in series with the secondary 107s of a feedback transformer 107. The primary 107p of transformer 107 is connected across the other diagonal of rectifier bridge in series with a synchronous A.-C. motor 106 representing the load, an alternating-current source 120 and a starting switch 117. The control circuit also includes phase-shifting means in the form of a variable shunt condenser 1241 and a series resistor .119.

Controlled rectifier is provided with a triggering circuit comprising a high-ohmic resistor 122, connected across the anode and the cathode of controlled rectifier 105, and a condenser .123 connected between a tap 122' on resistor .122 and the gate of rectifier 105. The voltage drop developed across resistor 122 will energize, via the suitably dimensioned capacitance 123, the gate of the controlled rectifier 105 and periodically fire the latter upon closure of switch 117. An alternating current W FIG. 6(a), then flows from source through a transi mission path including rectifier 102,-unidirectional control element 105 in its forward (anode-to-cathode) direction, rectifier 104 and load 106 during one half of the cycle, and through a second transmission path including rectifier 103, unidirectional control element 105 in the same direction, rectifier 10 1 and load 106 during the second half of the cycle, If the controlled rectifier 105 were to remain fully conductive throughout the entire cycle, the current flowing therethrough would have the wave form W FIG. 6( b). The load current would then also have the wave form W its amplitude depending upon the conductivity of the controlled rectifier 105.

In reality, however, the controlled rectifier 105 is periodically triggered by the pulsating current passing through resistor 12 2, the resulting voltage drop being opposed by a feedback voltage induced in the secondary 107s by a current flow through primary 107p of transformer 107. The phase shifter 119, 121 serves to adjust the output amplitude by advancing or retarding the firing point of rectifier 105, indicated at L in FIG. 6(0), which determines the location of the leading edge of each pulse of a wave W representing the actual Wave form of the current passed by the controlled rectifier 105. The end of the pulse occurs substantially at the end of each halfcycle of input wa-ve W Transformer 107, being in series with the load, tends to stabilize the amplitude of the current drawn by motor 106. The location of tap 122' and the capacitance of condenser 123 are so chosen as to fire the controlled rectifier 105 in the absence of feedback (i.e. upon the opening of the circuit of secondary 107s) at a point P FIG. 6(1)), at the foot of the leading edge of each pulse of Wave W the location of this point being determined by the resistance of the discharge path of condenser 123 which includes resistor 108 and part of resistor 12 2. The initial bias thus developed on the gate of rectifier 105 will then be augmented by the feedbackindu-ced voltage drop across resistor 108 which shifts the actual firing oint forwardly .or rearwardly from a point F, representing the firing point at normal load current, to determine the location of leading edge L of pulses W In FIG. 2 I show another embodiment of my invention comprising a rectifier bridge 200 containing rectifiers 201, 202, 203, 204. A thyratron 205 and a protective choke 216 are connected across one diagonal of the bridge; and a series-resonant circuit 210 is connected across the other diagonal in series with part of a parallel-resonant 3 network 212, an A.C. load 206 here shown as the horizontal sweep circuit of an oscilloscope, a source of alternating current 220, and a switch 217. Both resonant networks 210 and 212 are tuned substantially to the frequency of source 220. The primary 207p of a feedback transformer 207 is connected across load 206, the secondary 207s of that transformer constituting part of a feedback path including a potentiometer 218, bridged across a bias battery 209, a rectifier 224, and a grid-leak resistor 208 all serially connected between the grid and the cathode of thyratron 205. A condenser 223 is connected between a tap 222' on a high-ohmic variable resistor 222, which is bridged across the plate and the cathode of thyratron 205, and the grid of the thyratron, thus providing a triggering circuit similar to that described in connection with FIG. 1.

An alternating current W again flows from source 220 through bridge 200 when switch 217 is closed. A wave W FIG. 6(d), is thus fed into tuned circuits 210, 212 which function as harmonic-suppression means. The series-resonant network 210 and the parallel-resonant network 212 pass only substantially purely sinusoidal alternating current, eliminating all harmonics of the pulse train W to convert it into a sine wave W FIG. 6(a). Thyratron 205 is voltage-cont-nolled by the feedback circuit in which the voltage drop across load 206 induces a voltage in the secondary 207s which is fed back to the grid of the thyratron to supplement the biasing voltage from potentiometer 218 in opposition to the voltage tapped ofi from resistor 222, this action resulting in a stabilization of the load voltage, rather than of the load current as in the preceding embodiment. Quenching coil 216 insures the extinction of the thyratron 205, thereby restoring the control element to a non-conductive state as described hereinabove with respect to controlled rectifier 105.

In FIG. 3 I show a representation of a constant-current regulator system wherein an alternating-current source 320 is connected in series with a starting switch 317, an A.C. load 306 and the primary winding of a feedback transformer 307 across one diagonal of a rectifier bridge 300 whose rectifiers 301, 302, 303 and 304 are identical with their counterparts in the bridges 100 and 200.

- The anode and the cathode of a controlled rectifier 305 are connected across the positive and negative terminals of bridge 300. The triggering circuit for the gate of the controlled rectifier 305 comprises a transformer 340 whose primary winding 340p is connected across the A.C. source 320 after the switch 317 and which has a secondary winding 340s connected across the A.C. terminals of a rectifier bridge 324 in series with the load windings 338 of a saturable reactor 330. The saturable reactor 330 is also provided with a bias winding 337, in series with a variable resistor 335, which is energized from another secondary winding 340s of transformer 340 in the cadence of the alternating-current source 320 to promote the current flow through load windings 338. The secondary winding of the feedback transformer 307 is connected via a series resistor 334 across the control winding 333 of saturable reactor 330, the flux from winding 333 bucking that from winding 337 so as to tend to reduce the amplitude of the alternating current passing through bridge 324 from secondary 340s. The directcurrent terminals of the bridge 324 are shunted by a voltage-limiting device, here shown as a Zener diode 331 connected in series with a current-limiting resistor 332, and feed a differentiating circuit consisting of a small condenser 328 and a low-ohmic resistance 329. The output of the differentiating network is connected via a protective rectifier 325 across the gate and the cathode of controlled rectifier 305 while a high-ohmic resistance 326 returns the gate thereof to its cathode.

In operation, when switch 317 is closed the controlled rectifier 305 is triggered at the cadence of the alternatingcurrent input of the source 320, the position of the leading edge L of wave W FIG. 6(0), being determined by the impedance of the load windings 338 of the saturable reactor. The normal operating point is established by the setting of variable resistor 335 in the bias circuit of the reactor.

The periodic reduction of the inductance of the saturable reactor 330 by the differential action of windings 337 and 333 results in a pulsating output of rectifier bridge 300 which, but for the presence of Zener diode 331, would have the shape of a wave W as illustrated in dotted lines in FIG. 6(f). The Zener diode 331 serves to limit the amplitude of the pulsating direct current derived from the bridge 324, thereby permitting only a flat-topped wave W to pass to the differentiating network 328, 329. This network derives from the leading edge of each pulse of wave W a spike S, FIG. 6(g), which triggers the gate of controlled rectifier 305. The Zener diode 331, by clipping the leading edges of wave W limits the triggering spike S to an amplitude below the peak voltage capable of being tolerated by the rectifier gate.

The embodiment illustrated in FIG. 4 is a constantvoltage regulator circuit comprising a power transformer 440 whose primary winding 440 is connected across an A.C. source 420 in series with a starting switch 417. A secondary winding 440s of the transformer is serially con nected with an alternating-current load 406 between the A.C. terminals of a rectifier bridge 400 whose other diagonal contains the anode-cathode circuit of a controlled rectifier 405. The triggering circuit for the rectifier comprises a secondary winding 440s of transformer 440.

I The center tap of this winding forms the negative terminal of the triggering-circuit output while the outer limbs of winding 440s are connected through respective primary windings of a magnetic amplifier 430 to rectifiers 450, 450". The outputs of rectifiers 450 and 450 are tied together to form the positive terminal of the triggering circuit. A ballast resistor 441 bridges the positive and negative terminals of the circuit. These terminals are connected across a differentiating network 428, 429. The

\ latter is also connected across the gate and the. cathode 7 of controlled rectifier 405 via a rectifier 425 which prevents reverse surge currents from reaching the magnetic amplifier. A high-ohmic resistance 426 is connected between the cathode and the gate. A Zener diode 431, bridged in reverse direction across the output of differentiating network 428, 429, serves to limit the amplitude of the positive spikes S prior to their application to the gate of controlled rectifier 405.

The primary of a voltage-feedback transformer 407 is connected across the load 406 while its secondary winding is connected across the A.C. terminals of a rectifier bridge 424 whose pulsating D.-C. output passes through a smoothing or filtering network consisting of a resistor 446 and a condenser 445. A potentiometer 444 is connected across this D.-C. output. The control windings of the magnetic amplifier 430 are connected in series with the slider of the potentiometer 444, a Zener diode 443 poled to oppose the passage of the rectifier current from bridge 424, and a current-limiting resistor 442, and are returned to the negative terminal of the bridge 424.

In the absence of a feedback voltage of sufiicient magnitude to overcome the blocking effect of Zener diode 443, the pulsating output of the magnetic amplifier 430, amplitude-limited by the Zener diode 431 and converted into a spike S by the differentiating network 428, 429, fires the controlled rectifier 405 in the early part of each halfcycle of the alternatingcurrent input from source 420. The magnetic amplifier 430 may be of any of the wellknown types but, preferably, is self-saturating. When the voltage drop across the load 406 exceeds a predetermined limit, the Zener diode 443 breaks down to permit a flow of direct current through the control windings of magnetic amplifier 430, thereby reducing the saturation of its core to delay the firing of the controlled rectifier 405 and, therefore, to decrease the average current flow. through bridge 400 and load 406 until the desired load voltage is substantially re-established.

In FIG. 5 I show a regulator circuit for a direct current load, comprising a power transformer 540 whose primary winding 540p is connected across an alternating-current source 520 in series with a starting switch 517. A secondary winding 540s of the transformer is connected between the A.-C. terminals of a rectifier bridge 500. In the other diagonal of the bridge there are connected, in series, a controlled rectifier 505, a smoothing choke 560, and a direct-current load 506 such as a battery to be charged. The smoothing or filtering network also 1ncludes a condenser 561 bridged across the load 506. The triggering circuit for the controlled rectifier 505 is s milar to that of the preceding embodiment and comprrses a secondary winding 540s oftransformer 540 whose center tap forms the negative terminal of the triggerlng circuit and whose outer limbs are connected through respective load windings of a self-saturating magnetic amplrfier 530 to rectifiers 550', 550" thereof. The outputs of rectifiers 550' and 550" are tied together to form the positive terminal of the triggering circuit. A ballast resistor 541 bridges the positive and negative terminals of this circuit.

A two-terminal breakdown device such as a Zener diode 531 is connected in series with the current-limiting resistor 532 across the triggering-circuit terminals and across a differentiating network 528, 529 which feeds the gate-cathode circuit of controlled rectifier 505 through a rectifier 525, this diode functioning in the same manner as the Zener diode 331 of FIG. 3. A high-ohmic resistor 526 bridges the gate and the cathode of the rectifier 505. The control windings of the magnetic amplifier 530 are connected in series with the current-limiting resistor 542, a threshold device in the form of another Zener diode 543, and the slider of a potentiometer 544 which bridges the output of a filter network 545, 546 connected across the load 506.

In operation the controlled rectifier functions, generally as described with reference to FIG. 4, to supply a filtered direct current to the load 506. When, however, the voltage drop across the load exceeds a predetermined maximum, depending on the setting of potentiometer 544, the Zener diode 543 breaks down to permit a flow of current through the control windings of the magnetic amplifier, thereby reducing the saturation of the latter to delay the firing of the controlled rectifier 505. It is understood that rectifiers 401-404 (FIG. 4) and 501-504 (FIG. 5) are identical with their counterparts in the bridges 100, 200 and 300 of the previous figures.

While only a limited number of embodiments have been described and illustrated, it is to be understood that elements shown in certain embodiments could be combined with, or substituted for, features found in other embodiments to the extent of compatibility without the exercise of independent invention. These and other modifications should be readily apparent to persons skilled in the art intended to be embraced within the spirit and scope of the invention as defined in the appended claims.

I claim:

1. A circuit arrangement for producing a controlled flow of current through a load, comprising a driving circuit, a source of alternating current in said driving circuit, unidirectionally eifective electronic control means including a normally non-conductive breakdown device provided with an input electrode and circuit means coupling said electrode to said driving circuit for periodic triggering of said device into a conductive condition, a rectification network having a pair of alternating-current terminals connected in said driving circuit and further having a pair of direct-current terminals connected across said control means in the forward direction of the latter, biasing means for said control means coupled to said circuit means, and a feedback circuit for said biasing means connected together with said load in series with one of said pairs of terminals for delaying the triggering of said device and reducing the average current flow through said control means in response to increased flow of energy through said load, thereby stabilizing said flow of energy.

2. A circuit arrangement according to claim 1 wherein said feedback circuit includes voltage-responsive diode means for blocking the flow of feedback energy below a predetermined magnitude to said input electrode.

3. A circuit arrangement according to claim 2 wherein said feedback circuit is in series with said alternatingcurrent terminals, further including auxiliary rectifier means in said feedback circuit in series with said diode means.

4. A circuit arrangement according to claim 1 wherein said circuit means includes a transformer connected across said source, said biasing means including amplifier means connected to be energized from said transformer.

5. A circuit arrangement according to claim 4 wherein said amplifier means is provided with a saturable core, said feedback circuit comprising a winding on said core.

6. A circuit arrangement for producing a controlled flow of current through a load, comprising a source of alternating current, a driving circuit connected across said source, a full-wave rectification network having a pair of alternating-current teminals connected in said driving circuit and further having a pair of direct-current terminals adapted to develop a pulsating D.-C. voltage in response to the output of said source, an electronic breakdown device connected across said direct-current terminals, said device having an input electrode and being triggerable to conduct unidirectional current from said network upon the application of a firing potential of predetermined polarity to said electrode, one of said pairs of terminals being connected in series with said load, circuit means coupled with said source for deriving therefrom a control voltage in step with said pulsating D.-C. voltage, and differentiation means connected between said circuit means and said electrode for deriving from said control voltage a train of voltage spikes of said polarity and applying said spikes to said electrode during the occurrence of pulses of said D.-C. voltage whereby said device is maintained conductive for substantially the remainder of said pulses.

7. A circuit arrangement according to claim 6 wherein said circuit means includes biasing means for said electrode, further comprising a feedback connection between said driving circuit and said biasing means for enegizing the latter in a sense delaying the application of said spikes to said electrode in response to increased fiow of energy through said load, thereby stabilizing said flow of energy.

8. A circuit arrangement for producing a controlled flow of alternating current through a load, comprising a load circuit, a source of alternating current in said load circuit, a unidirectionally effective control element, a rectification network having a pair of alternating-current terminals connected across said load circuit and further having a pair of direct-current terminals connected across said control element in the forward direction of the latter, said control element comprising an electronic switch having an input connection coupled with said source for periodically triggering said switch into a conductive condition, said switch being adapted to remain conductive during the presence of a pulse of predetermined polarity passed by said control element and to return to a nonconductive condition upon the decay of said pulse, and a quenching inductance connected between said directcurrent terminals in series with said switch.

9. A circuit arrangement according to claim 8, further comprising adjustable phase-shifting means in said connection for regulating the load current by varying the interval of conductivity of said switch.

10. A circuit arrangement according to claim 8, further comprising harmonics-suppressor means in said load circuit.

11. A circuit arrangement according to claim 10 wherein said harmonics-suppressor means comprises a seriesresonant network tuned to the operating frequency of said source and serially inserted between said source and said rectification network.

12. A circuit arrangement acording to claim 11 wherein said harmonics-suppressor means further comprises a parallel-resonant network tuned to said opearting frequency and connected in cascade with said series-resonant network.

13. In a system for the energization of an A.-C. load, in combination, a source of alternating current in series with said load, a unidirectionally conductive electronic switch, first rectifier means between said source and said switch for converting the alternating output of said source into a pulsating current of a polarity passed by said switch, second rectifier means between said switch and said load for reconverting said pulsating current into an alternating load current, and circuit means for triggering said switch into a conductive condition substantially at the beginning of each pulse of said pulsating cur rent, said switch being adapted to remain conductive for the duration of such pulse and thereafter to return to a non-conductive condition.

14. The combination according to claim 13, further comprising harmonicsasuppressor means connected in series with said switch and said load for imparting a substantially sinusoidal shape to said load current.

15. The combination according to claim 13, further comprising reactance means energized by said source and coupled to said switch for positively restoring it to said non-conductive condition at the end of each pulse.

References Cited by the Examiner UNITED STATES PATENTS 2,275,308

3/42 Niemann 323-22 2,666,887 1/54 Rockafellow 32324 2,717,351 9/55 Christian 321l8 2,726,356 12/55 Rockafellow 32324 X 2,751,549 6/56 Chase 32322 2,767,365 10/56 Guggi 323--22 2,810,105 10/57 Henrich 32322 2,961,596 11/60 Rockafellow 32324 X 2,998,547 8/61 Berman 32322 3,010,062 1l/61 Van Emden 32322 3,040,239 6/62 Walker 32322 X OTHER REFERENCES Publication: Controlled Rectifiers Power Supply is Short-Circuit, Protected, Electronic Design; November 11, 1959.

LLOYD MCCOLLUM, Primary Examiner.

MILTON O. HIRSHFIELD, Examiner. 

1. A CIRCUIT ARRANGEMENT FOR PRODUCING A CONTROLLED FLOW OF CURRENT THROUGH A LOAD, COMPRISING A DRIVING CIRCUIT, A SOURCE OF ALTERNATING CURRENT INN SAID DRIVING CIRCUIT, UNIDIRECTIONALLY EFFECTIVE ELECTRONIC CONTROL MEANS INCLUDING A NORMALLY NON-CONDUCTIVE BREAKDOWN DEVICE PROVIDED WITH AN INPUT ELECTRODE AND CIRCUIT MEANS COUPLING SAID ELECTRODE TO SAID DRIVING CIRCUIT FOR PERIODEIC TRIGGERING OF SAID DEVICE INTO A CONDUCTIVE CONDITION, A RECTIFICATION NETWORK HAVING A PIR OF ALTERNATING-CURRENT TERMINALS CONNECTED IN SAID DRIVING CIRCUIT AND FURTHER HAVING A PAIR OF DIRECT-CURRENT TERMINALS CONNECTED ACROSS SAID CONTROL MEANS IN THE FORWARD DIRECTION OF THE LATTER, BIASING MEEANS FOR SAID CONTROL MEANS COUPLED TO SAID CIRCUIT MEANS, AND A FEEDBACKD CIRCUIT FOR SAID BIASING MEANS CONNECTED TOGETHER WITH SAID LOAD IN SERIES WITH ONE OF SAID PAIRS OF TERMINALS FOR DELAYING THE TRIGGERING OF SAID DEVICE AND REDUCING THE AVERAGE CURRENT FLOW THROUGH SAID CONTROL MEANS IN RESPONSE TO INCREASED FLOW OF ENERGY THROUGH SAID LOAD, THEREBY STABILIZING SAID FLOW OF ENERGY. 